Tensioning device for a traction mechanism, in particular a belt or a chain

ABSTRACT

A tensioning device for a traction mechanism, in particular a belt or a chain, is provided including a lever arm ( 2, 19 ) over which the traction mechanism is guided and on which a tensioning spring is arranged with its one end, the other end of the tensioning spring is arranged on a spring holder ( 6, 21 ), by which the tensioning device ( 1, 18, 30 ) can be fastened to an external object. A holding element ( 11, 22, 34 ), which extends from the lever arm ( 2, 19 ) to the spring holder ( 6, 21 ) and is detachably arranged on both said lever arm ( 2, 19 ) and said spring holder ( 6, 21 ), holds the tensioning device ( 1, 18, 30 ) in a position with a preloaded tensioning spring ( 4, 20, 33 ).

BACKGROUND

The invention relates to a tensioning device for a traction mechanism,in particular, a belt or a chain, comprising a lever arm over which thetraction mechanism is guided and on which a tensioning spring isarranged with its one end and whose other end is arranged on a springholder by which the tensioning device can be fastened to an externalobject.

Such a tensioning device is known, for example, from DE 195 01 685 C1.So that the assembly of this tensioning device is simplified, thetensioning device described there has a connection element that can beset in tension in the form of a spring band strip that extends from thespring holder to the lever arm, wherein a tensioning spring is providedin a known way between both the spring holder and the lever arm. Withthe lower end, the spring band strip is fixed on the spring holder by apin inserted into a borehole. The spring band strip passes through thetensioning spring in its interior and is guided by a spring support thatis provided on the lever arm and on which the tensioning spring issupported with its other end. On the end of the spring band strip,another pin that is engaged transversely is provided whose end isrotated by 90° to the strip longitudinal axis, so that a stop isproduced. In the assembled position, the upper pin is inserted andsupported on the tensioning lever. Because the length of the spring bandstrip is shorter than the length of the unloaded tensioning spring, thiscan thus be fixed conditionally in the pre-tensioned position by thetwo-sided pin support of the spring band strip.

Now if the tensioning device is installed, then the upper pin isremoved, so that the tensioning spring becomes unloaded. Then, inaddition to the pre-tensioning function, as a second function, themovement limiting of the tensioning spring path is given to the springband strip. This is because the tensioning spring can be unloaded onlyas far as the end of the spring band stop permits. If this runs, namely,against the tensioning lever, then the spring path is limited.

A disadvantage in this construction is, first, that it has a relativelyexpensive and complicated design with respect to the individual partsthat are used, in particular, as concerns the assembly. In addition, thespring band strip remains within the tensioning device or the helicalspring after removing the upper pin. If the stop is not contacted, thenthe spring band strip is not tensioned and consequently is movable, sothat it can vibrate, which possibly leads to the generation of noise.

SUMMARY

The invention is based on the objective of providing a tensioning devicethat allows the tensioning spring to be kept pre-tensioned, but that hasa simultaneously simple construction.

To meet this objective for a tensioning device of the type noted above,it is provided according to the invention that a holding element thatextends from the lever arm to the spring holder and that can be detachedfrom both is provided for holding the tensioning device in a positionwith the pre-tensioned tensioning spring.

In the tensioning device, the holding element is arranged detachably onthe lever arm as well as on the spring holder; thus, it can be removed.In addition, the holding element is a single piece and arranged orfastened on the appropriate part, that is, any external objects, such asconnection pins or the like are not required. This results in atensioning device that has a significantly simpler design and also amore economical production and that also does not tend to generate noiseduring operation after the holding element is removed.

According to a first construction of the invention, the holding elementis constructed as a pin that extends from the lever arm to the springholder and that has, on both ends, locking sections that are locked onthe lever arm and on the spring holder in the assembled position. Forreleasing the fixed position of the tensioning spring, the holdingelement that is tensioned by the spring tension is merely unloadedsomewhat and then released from its locked position on the lever arm andon the spring holder. This is easily possible during the installation ofthe tensioning device.

The pin itself preferably engages through the spring holder in acorresponding opening and extends through the tensioning spring and alsothrough or in a spring support provided on the tensioning lever. Withits other end, the tensioning spring is supported against this springsupport. The pin is then locked on the spring support. A force-optimizedlocking is also possible due to the orientation of the pin runningsomewhat axial with respect to the tensioning spring and also the springdirection.

The locking section of the pin provided on the end locked on the springsupport is preferably constructed in the form of a bend that can bebrought into a position engaging behind an abutment shoulder on thespring support by twisting the pin after it is inserted into or passedthrough the spring support. For assembly, when the tensioning spring iscompressed, the pin is merely to be guided through the spring holder andthe tensioning spring and into or through the spring support and thentwisted, for example, by ca. 90°, so that the bend on the end sideengages behind the abutment shoulder. In this way, the pin is locked onthis end. When the tensioning spring is relieved of pressure, theabutment shoulder is pressed against the bend and in this way limits thespring path in connection with the locking of the other pin end. Thelocking section of the pin that can be locked on the spring holder ispreferably realized in an improvement of the invention in the form of abend transitioning into a handle. This allows, first, the lockingsection to be constructed in a simple way and, second, the pin can beeasily moved and twisted and pulled out from the tensioning device.

In one alternative to the use of a pin, the holding element isconstructed as a tensioning band extending between the lever arm and thespring holder. The band itself is flexible, but in each case is mounteddetachably on the lever arm and also on the spring holder. For thispurpose, according to a first alternative of the invention, thetensioning band can form a ring and can be guided around a guide sectionon the lever arm and a guide section on the spring holder. For assembly,the lever arm and the spring holder are compressed, according to whichthe annular tensioning band is placed around the guide sections. Now ifforce is removed from the tensioning spring, then the spring path islimited by the tensioning band placed on the guide sections. Thetensioning band itself can be a metal or plastic band and is preferablyformed from a band section that is dimensioned accordingly in its lengthand whose ends are connected by an adhesive, crimped, or weldedconnection for the formation of the ring. For this purpose, a crimpingsleeve or the like can be used, as well as the two band ends beingeither welded together metallically or fused thermally for a plasticband.

The guide section provided on the tensioning lever is preferablyconstructed on a spring support holding the tensioning spring or else asa lateral projection directly on the tensioning section. The guidesection provided on the spring holder is preferably formed by the bottomside of the spring holder. In each case, the tensioning band also liessomewhat axial to the tensioning spring or to the spring forcedirection, so that here, despite fixation in the pre-tensioned state,none or only a negligible tilting moment is exerted on the spring.

In another alternative construction for use of a tensioning band, thisdoes not have an annular construction but instead holders are providedconnected on its two ends rigidly to the tensioning band, wherein, inthe assembled position, these holders are inserted and locked in holderreceptacles provided on the lever arm and on the spring holder. Theseholders can involve, for example, rigidly connected holding bolts or thelike that are inserted into correspondingly shaped receptacles on thelever arm or on the spring holder. The locking is here performed bycorresponding shaping of the holders and also their receptacles that canhave, for example, a round or triangular or some other shape in crosssection. Here, the assembly and disassembly is also extremely simple.All that is necessary is to compress the tensioning spring somewhat, inorder to insert or remove the tensioning band with its holders into orout of the receptacles. In this way, force is again removed from thetensioning spring.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantages and details of the invention will be describedbelow using embodiments with reference to the figures. The figures areschematic diagrams and show:

FIG. 1 is a schematic diagram of a first embodiment of a tensioningdevice according to the invention,

FIG. 2 is a schematic diagram of a second embodiment of a tensioningdevice according to the invention, and

FIG. 3 is a partial view of a third embodiment of a tensioning deviceaccording to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a tensioning device 1 according to the invention comprisinga tensioning lever 2 on which here a tensioning roller 3 is arranged. Inthe assembled position, a traction mechanism, primarily a belt, isguided over this tensioning roller. The tensioning device 1 furthercomprises a tensioning spring 4 that is constructed here as a helicalspring and is supported with its end facing the tensioning lever 2 on aspring support 5 that is connected rigidly to the tensioning lever 2 oris a part of the tensioning lever. The other end of the tensioningspring 4 is supported on a spring holder 6. The spring holder 6 isattached to an external object, for example, the motor vehicle engine orthe like, for which the attachment borehole 7 is used. Using thisborehole, the tensioning device is supported there so that it can pivot.Accordingly, the tensioning lever 2 also provides an attachment borehole8 with which it can be attached to an external object so that it canpivot.

Now, in order to be able to construct and deliver the tensioning device1 with a pre-tensioned tensioning spring, it is necessary to lock thetensioning spring 4 in the compressed state. Here, on the spring holder6 an elongated, essentially central opening 9 is provided. Acorresponding opening 10 is provided on the spring support 5. A holdingelement 11 in the form of a pin 12 is guided through the openings 9 and10 and also through the helical spring 4. On its end facing thetensioning lever 2, the pin 12 has a bend 13 that forms a lockingsection. On the opposite end, another bend 14 is provided thattransitions into a handle 15. The pin 9 is now guided through theopening 9 with the end having the bend 13, wherein for passing through,the pin 12 is turned by ca. 90° with respect to the position shown inFIG. 1. That is, the opening 9 as well as the opening 10 have anelongated construction viewed in cross section, so that the pin with thebend 13 can be pushed through. The width, however, in particular, of theopening 10, is dimensioned so that the pin can no longer slide throughwhen it is rotated to the position shown in FIG. 1. The pin 12 is firstpushed through the opening 9, through the tensioning spring 4, and thenthrough the opening 10 and then turned by ca. 90° to achieve theposition shown in FIG. 1. In this position, the bend 13 engages anabutment shoulder 16 that is provided on the spring support 5 or isformed by the free, upper support surface. Now, if this holding force isremoved from the tensioning spring 4, it forces the tensioning lever 2and the spring support 6 apart. Here, the bend 13 contacts the abutmentshoulder 16, while the bend 14 contacts the contact side 17 of thespring holder 6. In this way, the spring path is limited. The tensioningspring 4 can be locked in the pre-tensioned position.

For releasing the lock, the pin 12 merely has to be unloaded somewhat,so that it can be turned back by 90° using the handle 15 and can then beremoved again from the opening 10, the helical spring 4, and also theopening 9.

FIG. 2 shows another tensioning device 18 according to the invention,similarly comprising a tensioning lever 19, a tensioning spring 20, andalso a spring holder 21. The function and the basic constructioncorrespond to what was described with respect to FIG. 1.

Here, a holding element 22 is also provided for fixing the tensioningdevice 18 with a pre-tensioned tensioning spring 20. This holdingelement 22 is here constructed in the form of an annular tensioning band23 that can be made from plastic or metal. The tensioning band 23 thatis made from an elongated band section, whose band ends are fixedtogether by a crimping element 24 in the illustrated embodiment, thusclosing the tensioning band into an annular shape, that is guided arounda guide section 25 on the tensioning lever and also a guide section 26on the spring holder 21. The guide section 25 on the tensioning leverprojects laterally. It forms the spring support 27 by itself or such apart is attached to it. The tensioning spring 20 is supported againstthis spring support 27. The guide section 25 is formed by the outside ofthis projection 28. The outside has a curved construction.

The guide section 26 on the spring holder 21 is formed by the outersurface of the bottom side 29 of the spring holder 21 opposite the sideon which the tensioning spring 20 is supported. This outer surface 29also has a round construction.

Now, for assembling the tensioning band 23, the tensioning device 18 ispressed together. Therefore, the tensioning spring 20 is compressed.Then the already closed tensioning band 23 is placed around the guidesections 25 and 26, after which force is removed from the tensioningspring 20 again and the tensioning band 23 is clamped, here, however,limiting the spring path. For detaching the tensioning band 23, thetensioning spring 20 is merely compressed somewhat again, after whichthe tensioning band 23 can be easily removed by hand. It would also benatural to separate the tensioning band with shears or pincers. Then,however, it cannot be reused.

FIG. 3 finally shows another embodiment of a tensioning device 30according to the invention in a partial view, wherein here only asection view through the spring holder 31 and the spring support 32 isshown. Also here, for fixing the pretensioned tensioning spring 33, aholding element 34 is used in the form of a tensioning band 35. However,non-detachable, end holders 36 that are constructed with a T-shapedcross section are provided on this holding element. On the spring holder31 and on the spring support 32 there are correspondingly shaped holderreceptacles 37 in which the holders 36 can be inserted from the side. Inthis way, the tensioning spring 33 can also be fixed in thepre-tensioned position, according to which the tensioning band 35 lockedby the holders 36 limits the movement path. For release, the tensioningspring 33 is merely compressed somewhat and the holders 36 are pulledout from the holder receptacles 37 that are open on the side.

Finally, it is to be stated that the term “tensioning band” is to beunderstood generally and comprises not only flat bands, but also, e.g.,a cord made from, e.g., plastic or a wire strand, or the like, closedinto a ring.

REFERENCE NUMBERS

-   -   1 Tensioning device    -   2 Tensioning lever    -   3 Tensioning roller    -   4 Tensioning spring    -   5 Spring support    -   6 Spring holder    -   7 Attachment borehole    -   8 Attachment borehole    -   9 Opening    -   10 Opening    -   11 Holding element    -   12 Pin    -   13 Bend    -   14 Bend    -   15 Handle    -   16 Abutment shoulder    -   17 Contact side    -   18 Tensioning device    -   19 Tensioning lever    -   20 Tensioning spring    -   21 Spring holder    -   22 Holding element    -   23 Tensioning band    -   24 Crimping element    -   25 Guide section    -   26 Guide section    -   27 Spring support    -   28 Projection    -   29 Outer surface    -   30 Tensioning device    -   31 Spring holder    -   32 Spring support    -   33 Tensioning spring    -   34 Holding element    -   35 Tensioning band    -   36 Holders    -   37 Holding receptacles

1. Tensioning device for a traction mechanism, comprising a lever armover which the traction mechanism is guided and on which a tensioningspring is arranged with one end and a second end of which is arranged ona spring holder by which the tensioning device can be attached to anexternal object, a holding element extends from the lever arm to thespring holder and is arranged detachably at both ends to hold thetensioning device in a position with the tensioning springpre-tensioned.
 2. Tensioning device according to claim 1, wherein theholding element is a pin that extends from the lever arm to the springholder and has locking sections on both of the ends that are locked inan assembled position on the lever arm and on the spring holder. 3.Tensioning device according to claim 2, wherein the pin is guidedthrough the spring holder and the tensioning spring and through or in aspring support provided on the tensioning lever, wherein the pin islocked on the spring support.
 4. Tensioning device according to claim 3,wherein the locking section provided on the end locked on the springsupport is constructed as a bend that can be brought into a positionengaging behind an abutment shoulder on the spring support throughrotation of the pin after insertion into or the pin having passedthrough the spring support.
 5. Tensioning device according to claim 4,wherein the locking section of the pin that can be locked on the springholder is formed by a bend transitioning into a handle.
 6. Tensioningdevice according to claim 1, wherein the holding element is constructedas a tensioning band that extends between the lever arm and the springholder.
 7. Tensioning device according to claim 6, wherein thetensioning band forms a ring and is guided around a guide section on thelever arm and a guide section on the spring holder.
 8. Tensioning deviceaccording to claim 7, wherein the tensioning band is formed by anadhesive, crimped, or welded connection into a peripheral ring band. 9.Tensioning device according to claim 7, wherein the guide sectionprovided on the tensioning lever is constructed on a spring supportholding the tensioning spring.
 10. Tensioning device according to claim7, wherein the guide section provided on the spring holder is formed bya bottom side of the spring holder itself.
 11. Tensioning deviceaccording to claim 6, wherein on both ends on the tensioning band, thereare holders that are inserted and locked in an assembled position inholder receptacles provided on the lever arm or a spring supportprovided on the lever arm and on the spring holder.
 12. Tensioningdevice according to claim 6, wherein the tensioning band is made frommetal or plastic.